Get all values of a specific column in a multidimensional array [duplicate] - php

Question

This question already has answers here:
How to get an array of specific "key" in multidimensional array without looping [duplicate]
(4 answers)
Closed 1 year ago.
I have a multidimensional array, that has say, x number of columns and y number of rows.
I want specifically all the values in the 3rd column.
The obvious way to go about doing this is to put this in a for loop like this
for(i=0;i<y-1;i++)
{
$ThirdColumn[] = $array[$i][3];
}
but there is an obvious time complexity of O(n) involved here. Is there a built in way for me to simply extract each of these rows from the array without having to loop in.
For example (this does not work offcourse)
$ThirdColumn = $array[][3]

Answer 1

Given a bidimensional array $channels:
$channels = array(
array(
'id' => 100,
'name' => 'Direct'
),
array(
'id' => 200,
'name' => 'Dynamic'
)
);
A nice way is using array_map:
$_currentChannels = array_map(function ($value) {
return $value['name'];
}, $channels);
and if you are a potentate (php 5.5+) through array_column:
$_currentChannels = array_column($channels, 'name');
Both results in:
Array
(
[0] => Direct
[1] => Dynamic
)
Star guests:
array_map (php4+) and array_column (php5.5+)
// array array_map ( callable $callback , array $array1 [, array $... ] )
// array array_column ( array $array , mixed $column_key [, mixed $index_key = null ] )

Answer 2

Is there a built in way for me to simply extract each of these rows from the array without having to loop in.
Not yet. There will be a function soon named array_column(). However the complexity will be the same, it's just a bit more optimized because it's implemented in C and inside the PHP engine.

Answer 3

Try this....
foreach ($array as $val)
{
$thirdCol[] = $val[2];
}
Youll endup with an array of all values from 3rd column

Answer 4

Another way to do the same would be something like $newArray = array_map( function($a) { return $a['desiredColumn']; }, $oldArray ); though I don't think it will make any significant (if any) improvement on the performance.

Answer 5

You could try this:
$array["a"][0]=10;
$array["a"][1]=20;
$array["a"][2]=30;
$array["a"][3]=40;
$array["a"][4]=50;
$array["a"][5]=60;
$array["b"][0]="xx";
$array["b"][1]="yy";
$array["b"][2]="zz";
$array["b"][3]="aa";
$array["b"][4]="vv";
$array["b"][5]="rr";
$output = array_slice($array["b"], 0, count($array["b"]));
print_r($output);